b737-200 adv

[tbaylx]

Trying to figure out a problem and am stumped.

The 737 engine bleed valves are AC powered from the respective AC Transfer Buses. The starter valves are engine side of the engine bleed valves, so the engine bleed valves need to be open to allow pneumatics to get to the starter valves.

If the engine bleed valves were closed and you didn't have AC power available (no apu or gpu) is there a alternate way to open the engine bleed valves to allow a start?

[FlightPathOBN]

There are a few with gravel kits running around in Alaska...

[tbaylx]

Yeah i thought so too, but stby power only powers the ac stby bus, not the transfer buses.

It's a operator in canada called canadian north. Still running 10 of the old birds up into the arctic off gravel and pavement.

[sevenstrokeroll]

mind you its been awhile and I don't have my manual handy.

but if you don't have apu or gpu , what is your pneumatic source to spin the starter?

and if you do have a pneumatic source, I do seem to recall that a mechanic can manually open and close the valve from outside, under direction of the pilot via intercom.

I can recall one start I did with external pneumatic, and ship's battery only...what a chore, we had to tell the mechanic when to open and close the valve. of course once one engine was running we had AC from eng gen and then did a cross bleed start.

does this help?

[JammedStab]

Why would you even want to start an engine if there was no AC power available on it......? :confused:





You want to start the engines so you can get out of where you are and proceed to destination or maintenance base. Remember, you may be in a remote location. 737 operators in northern Canada operate to some remote locations including ice strips on occasion. If you lose your APU generator, you have a problem. Once one engine is started, you have AC power again.

I would think that this might be a situation requiring a battery start or some location with the same problem but the one AC GPU is broken as well.

[Bob Lenahan]

Several companies running 732's in Mexico.

[vapilot2004]

AC power is not required on the -200 if the engine bleed valve was left open at last shutdown. Battery bus provides electrical power for the start valve solenoid & ignition.

Ah, but you have a closed bleed valve? Call a ground engineer for a manual override. Afterwards, cross bleed starts are possible, but fairly noisy on the old gal since you've generally got to go to 75% or better N2 for adequate start pressure.

[JammedStab]

That is correct. It is standard procedure to leave the bleed valves open on shutdown in case battery start is subsequently required. Moter operated valves I would say.

[FlightPathOBN]

blast from the...well..past...

http://www.flightglobal.com/airspace/media/galleries/images/60140/500x400/canadian-north-c-gdpa-737-200-combi-with.JPG

[aviatorhi]

As has already been said, always leave your bleed valves open before shutting down. Then the worst thing that can happen is you need a long screwdriver to start the airplane, not opening up the panels and manually forcing bleed valves open.